JP3044257B2 - Driving device for switching element - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching power supply device and a driving device for a switching element used in a chopper circuit.

[Conventional technology]

For example, there is a method in which a power device is driven by a multivibrator in one of the driving devices. In this method, a configuration is usually adopted in which a multivibrator is used as a signal output circuit, a drive circuit is operated based on the output signal, and the power element is driven by the drive circuit.

The driving circuit is provided between the multivibrator and the power element for the following reason.

Since the input impedance of the electronic element is low and capacitive, the transient characteristics of the multivibrator are extremely poor.

If the electronic device is a bipolar transistor, the base
In the variation range of the voltage V _BE between the emitters positive direction, usually, 0.7
It is limited to about 1.2V. Therefore, the dynamic range of the output end of the multivibrator is limited, and the amount of feedback to the other multivibrator output element is reduced. For this reason, not only the transient characteristics of the multivibrator may deteriorate, but also the multivibrator may fall into an inoperable state.

For this reason, it is desirable that the drive circuit has good transient characteristics, high input impedance, and low output impedance. In other words, the drive circuit is required to have excellent frequency characteristics and response characteristics, and to have the functions of an impedance conversion and current amplification circuit.

FIG. 5 is a circuit diagram showing an example of a conventional driving device for a switching element.

A drive circuit 3 is usually connected to a power element 1 as a switching element via a current limiting resistor 2, and a multivibrator 4 is connected to the drive circuit 3.

The drive circuit 3 is a PNP whose emitter is connected to the + power supply V _Sp
A transistor 101 and an NPN transistor 102 whose emitter is connected to the -power supply V _Sn are used in an output stage, and a commonly connected collector is an output terminal. The base of the transistor 101 is connected to the input terminal through a parallel circuit of a resistor 103 and a capacitor 104.
Is connected to the input terminal via a parallel circuit of a resistor 105 and a capacitor 106.

The multivibrator 4 has two polarities and the same specifications.
One of built around transistors 201 and 202, resistors 203 and 204 is connected between each collector and + supply V _Sp. Further, the resistance between each of the base and + supply V _SP 209 and 210
Is connected. The emitters of the transistors 201 and 202 are commonly connected and connected to the _-power supply V _Sn . A parallel circuit of a resistor 205 and a capacitor 206 is inserted between the base of the transistor 201 and the collector of the transistor 202.A parallel circuit of a resistor 207 and a capacitor 208 is inserted between the base of the transistor 202 and the collector of the transistor 201. Is inserted.

In the above structure, a state in which the transistor 201 is turned on and a state in which the transistor 202 is turned on are alternately repeated at a constant cycle. In this circuit, the time constant at the time of charging is determined by the combination of the resistor 203 and the capacitor 208 and the combination of the resistor 204 and the capacitor 206, and the capacitor 206, the resistor 205 and the resistor 209 and the capacitor 208, the resistor 207 and the resistor 210
Determines the time constant at the time of discharge. The time constant at the time of charging is extremely short, while the time constant at the time of discharging is long.

For example, the transistor 202 the transistor 201 is on is the off, the transistor 201 base voltage is substantially zero state, the base voltage of the transistor 202 by the discharge of the capacitor 208 attempts to rise gradually V _SP from a negative potential . When the potential becomes 0 in the middle, the transistor 202 is turned on and the transistor 201 is turned off.

After that, the transistor 201 and the transistor 202 alternately repeat the on / off operation, and a fixed cycle (the resistor 205, the resistor 20)
9, a cycle determined by the time constant of the capacitor 206 and the time constants of the resistor 207, the resistor 210, and the capacitor 208).

The output voltage of the multivibrator 4 is applied to the drive circuit 3, amplified by the transistors 101 and 102, and applied to the base of the power element 1 via the resistor 2. Power element 1 controls energization of a primary side of a transformer (not shown).

This type of circuit has a characteristic that good efficiency can be obtained even at a high switching frequency.

[Problems to be solved by the invention]

However, in the above-described prior art, there is a problem that the number of circuit stages is increased, the number of partial points is increased, and the power consumption by the multivibrator and the drive circuit is large.

SUMMARY OF THE INVENTION An object of the present invention is to provide a driving device for a switching element which can reduce the number of circuit stages and can be driven with low power consumption.

[Means for solving the problem]

In order to achieve the above object, according to the present invention, a basic circuit of a multivibrator is configured using first and second transistors having the same polarity, and a driving device that drives a power element using one of its collector outputs is provided. In the apparatus, a collector is connected to the first transistor so that a common collector current flows, and a third transistor is connected between a collector of the second transistor and a control terminal of the power element. A first inductive element connected to the first inductive element and a winding end having the same polarity in voltage connected to the output side of the inductive element, and the other winding end connected to the first and the second through a diode.
A second inductive element connected to a power supply having a polarity opposite to that of the connection power supply of the second transistor and commonly using the wound core material of the first inductive element; A first method for making the amount of feedback in the reverse direction asymmetric with respect to the amount of feedback from the collector to the bases of the first and third transistors.
And the second feedback means for supplying the collector output of the first transistor to the base of the second transistor.

[Action]

According to the above means, a pair of transistors of the same polarity, whose emitters are connected to each other (or equivalent configuration),
The third transistor connected to the collector of one of the transistors forms a multivibrator. The first and third transistors have two metastable states, on-off and off-on, and oscillate by alternately repeating this state at a constant cycle. The charge and discharge time of the capacitor connected to the base of the third transistor is determined. Furthermore, the second
By connecting an inductive element to the collector of the transistor and performing feedback from the connection point to the bases of the first and third transistors, the impedance seen from the second transistor is increased, and the dynamic range is improved. In addition, the inductive element functions to limit the output current of the power element. Therefore, the power element can be directly driven by the multivibrator without the intervention of the drive circuit. Therefore, a simple and low-loss drive device for the switching element can be obtained.

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a first circuit diagram showing a principle configuration of a driving device for a switching element according to the present invention. In FIG. 1, the same components as those shown in FIG. 5 are denoted by the same reference numerals, and a duplicate description will be omitted below.

The emitter of a PNP transistor 11 (first transistor) and the emitter of a transistor 12 (second transistor) are connected to the + power supply, and the collector of the transistor 11 is connected to the NPN
The collector of the transistor 13 is connected, and the emitter is connected to the negative power supply. The transistor 13 and the transistor 11 form a totem-pole type circuit. One end of a primary winding (L _P ) of a transistor 14 serving as a first inductive element is connected to a collector of the transistor 12, and the other end is connected to a base (control terminal) of the power element 1. One end base (an emitter of the power device 1 of the secondary winding (L _S) of the transformer 14 is a second inductive element -
Power supply), and the other end is diode 15,16
Is connected to the power supply.

A parallel circuit of a resistor 17 and a capacitor 18 is connected between the base of the transistor 12 and the transistor 11. One end of a parallel circuit of a resistor 19 and a capacitor 20 is connected to the base of the transistor 11, the other end is connected to one end of a parallel circuit of a capacitor 21 and a zener diode 22, and the other end is connected to the collector of the transistor 12. Have been. Furthermore, a resistor 59 is connected, and the other end is connected to V _sn
(-).

Further, one end of a parallel circuit consisting of a resistor 23 and a capacitor 24 is connected to the base of the transistor 13, one end of a parallel circuit consisting of a capacitor 25 and a Zener diode 26 is connected to the other end, and the other end of the transistor 12 Connected to collector. Furthermore, a resistor 58 is connected,
The other end is connected to V _SP (+).

Next, the operation of the embodiment having the configuration shown in FIG. 1 will be described.

In this embodiment, the transistors 11 and 13 are the resistors 19, 59, the capacitor 20 and the resistors 23, 58, and 24.
Oscillates by alternately turning on and off according to the time constant determined by The transistor 13 forms a pair with the transistor 11, and has (13) on / (11) off and (13) off /
(11) An operation having two metastable states of ON is performed.

Here, for example, when the transistors 13 and 12 are on and the transistor 11 is off, the base voltage of the transistor 13 is almost 0 (“0.7”). Due to the discharge of the capacitor 20, the base voltage of the transistor 11 gradually increases from the positive potential.
Attempts to descend to V _Sn (-). In this process, discharging is performed in the path of the capacitor 20 → the resistor 59 → V _Sn (−) → V _SP (+) → the transistor 12 → the capacitor 20.

When the voltage between the emitter and the base of the transistor 11 becomes 0 “substantially 0 (0.7)” during this discharging, the transistor 11 is turned on, and at the same time, the transistors 12 and 13 are turned off. The base voltage of the transistor 11 is
Base → Zener diode 22 → primary winding of transformer 14 → secondary winding → diodes 15, 16 → power supply V _Sn .

On the other hand, when the transistor 13 is on, a base current is supplied to the transistor 12 via the resistor 17, but the base current flows instantaneously due to the presence of the capacitor 18, and the transistor 12 is turned on. When the transistor 12 is turned on, its base current is supplied to the power element 1 via the primary winding of the transformer 14 by the collector current, and the power element 1 is turned on. This on state is connected until the transistor 12 is turned off.

In FIG. 1, in order to prevent malfunctions due to kick-off of the capacitors 18 and 20 when the transformer 14 emits flyback energy, the zener diodes 22 and 2 are used.
6 is provided to provide feedback.

As described above, in the present embodiment, the primary winding of the transformer 14 is connected to the collector of the transistor 12,
Since feedback to the transistors 13 and 13 is performed from the collector of the transistor 12 and the output is taken out from the temporary winding and the secondary winding, the multivibrator and the power element 1 can be directly connected. Can be reduced.

Next, the characteristic operation of the configuration shown in FIG. 1 will be described in detail.

First, the first feature will be described. Since the connection point p between the primary winding L _P and the secondary winding L _S is directly connected to the base of the power element 1, its potential is equal to the base potential of the power element 1. Therefore, the dynamic range at the point p is limited to a narrow range of a value obtained by subtracting V _Sn from the voltage between the base and the emitter of the power element 1. Further, since the impedance between the base and the emitter of the power element 1 is low, sufficient feedback cannot be obtained when feedback is performed from the point p to the transistors 11 and 13. For this reason, the transient characteristics of the multivibrator due to the ton transistors 11, 12 become extremely poor, and in some cases, the operation as a multivibrator becomes impossible.

In contrast, q point of the collector of the transistor 12, by inserting a temporary winding L _P suitable value, the impedance seen from the collector of the transistor 12 is increased,
It becomes more dynamic range for most (V _SP -V _Sn). Therefore, the feedback from the point q to the transistors 11 and 13 is
Both the coefficient and the amount have sufficient values, and a multivibrator having good characteristics can be obtained.

Next, (the output current is limited by transient winding L _P) second feature will be described.

Here, the base current of the power element 1 is I _B4 , the base-emitter voltage is V _BE4 , the collector-
The emitter-to-emitter voltage is V _CE2 , the on time of power element 1 is t _on ,
Assuming that the inductance of the primary winding L _P is L _P , the power element 1
Maximum current I _B4 (max) is expressed by the following equation.

I _B4 (max) = ｛(V _SP −V _Pn ) −V _CE2 −V _BE4 ｝ t _on / L _P (1) Here, V _CE2 is usually small enough to be ignored.
Equation (1) is as follows.

_{I B4 (max) = {(} V SP -V Pn) -V BE4} t on / L P ··· (2) Thus, within the scope of the primary winding L _P of a preferred feedback condition (2) of (V _SP −V _Pn )
The required I _B4 (max) can be output.

By the way, in order to output a current sufficient to drive the power element 1, the transistor 12 must have a corresponding current capacity (I _C ) and power capacity (P _C ). On the other hand, the transistors 11 and 13 need only output the current required to output the current required for the input of the transistor 12. The maximum output current (I _c max) and the maximum power consumption (P _c max) of the transistor 12 are 1 / h _fe in each _operating state.
(However, h _fe is the current amplification factor) is sufficient. Normally, smaller transistors are more readily available at higher speeds and are less expensive. Therefore, as shown in FIG. 1, asymmetrical circuits as shown in FIG. 1 have the advantage of improving performance and reducing costs at the same time.

Note that, in the above embodiment, an example in which a PNP type is used for the transistor 12 is shown. However, as shown in FIG. 6, an NPN type can be used. In this case, connected to the transformer 14 to V _SP side, the transistor 12 to the power device 1 side (the emitter connected to the base of the power device 1, the collector is connected to the low potential side of the transformer 14) to connect to.

Next, a specific embodiment of a driving device for a switching element according to the present invention will be described with reference to FIGS. 2, 3, and 4. FIG.

FIG. 2 is a circuit diagram showing a first embodiment of the present invention. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and a duplicate description will be omitted.

This embodiment, with respect to configuration of FIG. 1, the resistor 27 and the resistor 28 is inserted between the collector and a power supply V _SP of each of the transistors 11 and transistor 12, transistor 11,
Resistors 29, 30, and 31 are connected between the bases 12 and 13 and the emitter side to ensure the bistable operation.
In addition, by setting the resistors 27 and 28 to small resistances and selecting the resistors 17 and 19 to appropriate values, it is possible to make the current when each of the transistors 11 and 12 is in operation slightly saturated.
Thus, 2 of the collector of the V _SP and transistors 11 and 12
The terminal impedance can be increased.

Further, the anode of a diode 32 is connected to the base of the transistor 11, a diode 33 is connected between the cathode of the diode 32 and the power supply _VSP, and a connection point of the two diodes is a pulse signal via a capacitor 35. Is applied. Similarly, the cathode of a diode 36 is connected to the base of the transistor 13, and a diode 37 is connected between the anode of the diode 36 and the power supply V _Sn.
A pulse signal is applied to a connection point of the two diodes via a capacitor 38. Diodes 32 and 33 and diode 3
Each of 6, 37 forms a waveform shaping circuit.

Since the entire operation of the embodiment shown in FIG. 2 is the same as that of the basic circuit shown in FIG. 1, the description is omitted here.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention. The present embodiment is characterized in that it operates as a monostable multivibrator. The stable state is set to either conduction or non-conduction of the power element 1, and the power element 1 is inverted by a signal, and the inversion time (the delay time is changed by the bias current). In this embodiment, the same reference numerals are used for the same components as those shown in FIGS.

In this embodiment, connected to a power supply V _SP cathode emitter and diode 16 of the power element 1 through a resistor 39.
This resistor 39 is for current detection, and the power supply _VSP has a reference voltage E
_S1 is connected, the positive-phase input terminal of the reference voltage the operational amplifier 41 via a resistor 40 to E _S1 is connected, the reverse phase input terminal connected to the emitter of the power device 1 through a resistor 42. Further, a resistor 43 is connected between the negative-phase input terminal and the output terminal. The output terminal of the operational amplifier 41 has an AND gate
One input terminal of 44 is connected.

A reference voltage _ES2 is connected to the power supply _VSP , and this voltage is connected to the positive-phase input terminal of the operational amplifier 46 via the resistor 45,
An external control signal is applied to the opposite-phase input terminal via a resistor 47. In addition, a resistor 48 between the negative-phase input terminal and the output terminal
The output signal of the output terminal is applied to the positive-phase input terminal of the operational amplifier 41 via the resistor 49. Furthermore, between the output terminal and the power supply V _SP of the operational amplifier 46, resistors 50 and 51 are connected in series, the resistor 52 between the base of the intermediate connection point and the transistor 13 are connected. In addition, AND Gate 44
A delay circuit 53 is inserted and connected between the other input terminal and the collector of the transistor 13. Also transistors
A resistor 54 is connected between the base 12 and V _Sn .

According to the configuration of FIG. 3, the base bias current of the transistor 13 is changed by the voltage obtained by the voltage division of the resistors 50 and 51, so that the non-conduction time of the transistor 13 can be mainly changed. The width of the is adjusted. Also, as the external control signal applied to the operational amplifier 46, if the output of the error amplifier for output adjustment on the secondary side of the transformer 14 is connected, the reference voltage of the operational amplifier 41 can be increased even if the output increases or an overcurrent occurs. Work to lower the At the same time, the non-conduction time of the transistors 12 and 13 becomes longer, and control to shorten the conduction time of the transistor 11 becomes possible.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention. Also in the present embodiment, the same reference numerals are used for the same components as those in FIGS. 1, 2 and 3, and duplicate description will be omitted.

This embodiment, operational amplifier 41 from the configuration of FIG. 3, the AND gate 44, delay circuit 53, and to remove the waveform shaping circuit of the input side of the transistor 11, the resistance between the resistor 50 and the power source V _Pn 5
5. A configuration is such that a resistor 56 is connected in series, and a resistor 57 is connected between a connection point between the resistors 55 and 56 and the base of the transistor 11.

Also in this configuration, the divided voltage output by the resistors 51 and 52 is
By changing the base current of the transistor 11 and adjusting the ON width of the power signal, the conduction time of the power element 1 is mainly controlled. On the other hand, the divided voltage output by the resistors 55 and 56 functions as a bias circuit that changes the bias current flowing through the resistor 57, adjusts the off width of the output signal, and mainly controls the non-conduction time of the power element 1. This change is obtained by changing a constant within a certain range of the duty of the power element 1.
Although it can be changed almost differentially, when the limit is exceeded, only one of the conduction time and the non-conduction time tends to increase. This means that if the constant is set so as to be differential with the duty to obtain the desired output, it is necessary to reduce the output (overvoltage, overcurrent), and when the limit of the reduction of the conduction time is exceeded, This means that the time is extended and frequency modulation is performed, so that the output can be extremely narrowed.

In FIG. 4, the resistor 57 is connected to V _Sn
As shown in the figure, by providing an operational amplifier 41, an AND gate 44, a delay circuit 53, and a resistor 39 and providing a conduction signal (pulse) to the transistor 11, the conduction signal time for the power element 1 is reduced. Of the resistor 40
In the range longer than the time when the output voltage reaches the reference voltage, the non-stabilized multivibrator operates like a monostable multivibrator.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, a basic circuit of a multivibrator is constituted by using first and second transistors having the same polarity, and a driving device for driving a power element by using one of the collector outputs. In the apparatus, a collector is connected to the first transistor so that a common collector current flows, and a third transistor is connected between a collector of the second transistor and a control terminal of the power element. A first inductive element connected to the first inductive element, a winding end of the same voltage polarity is connected to the output side of the inductive element, and the other winding end is connected via a diode to the first inductive element.
A second inductive element connected to a power supply having a polarity opposite to that of the connection power supply of the second transistor, and commonly using the wound core material of the first inductive terminal; A first method for making the amount of feedback in the reverse direction asymmetric with respect to the amount of feedback from the collector to the bases of the first and third transistors.
And a second feedback means for supplying the collector output of the first transistor to the base of the second transistor, so that a simple and low-loss driving device can be provided without deteriorating the characteristics. Can be configured.

[Brief description of the drawings]

FIG. 1 is a first circuit diagram showing a principle configuration of a switching device driving device according to the present invention, FIG. 2 is a circuit diagram showing a first embodiment of the present invention, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a circuit diagram showing a third embodiment of the present invention, FIG. 5 is a circuit diagram showing an example of a conventional driving device for a switching device, and FIG. 6 is a circuit diagram showing a switching device according to the present invention. FIG. 3 is a second circuit diagram illustrating a basic configuration of the driving device. 1 ... power element, 11, 12, 12 ', 13, 101, 201, 202 ... transistor, 14 ... transformer, 15, 16, 32, 33, 36, 37 ... diode, 17, 19, 23, 27, 28, 29, 30,31,39,50,51,52,55,5
6,57,58,59,103,105,203,204,205,207 …… resistance, 18,20,
21,24,25,35,38,104,106,206,208 …… Capacitor, 22,2
6… Zener diode, 41,46 …… Operational amplifier, 44…
... AND gate, 53 ... delay circuit, _VSP , V _Sn , V _Pn ... power supply, E _S1 , E _S2 ... reference voltage.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Masae Sugawara Inventor Masamichi Sugawara, Shibata-cho, Miyagi Prefecture, 3rd name, Shinmei-do, Tomei Ricoh Co., Ltd. (72) Inventor Tsuneo Ikegami Ichibancho, Aoba-ku, Sendai City, Miyagi Prefecture 1-14-6 (72) Inventor Shigeo Takagi 1110 Hirai-cho, Tochigi-city, Tochigi Prefecture (56) References JP-A-61-247275 (JP, A) JP-A 60-82986 (JP, U) JP-A 58 -152032 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H03K 3/30 H02M 3/00 H02M 3/28

Claims (1)

(57) [Claims] 1. A driving device for forming a basic circuit of a multivibrator using first and second transistors having the same polarity, and driving a power element using one collector output of the multivibrator. A third transistor having a collector connected to the transistor, a first inductive element connected between a collector of the second transistor and a control terminal of the electronic element, A winding end having the same polarity in terms of voltage is connected to the output side, and the other winding end is connected via a diode to a power supply having a polarity opposite to that of the connection power supply of the first and second transistors, and Second using the wound core material of the inductive element of
An inductive element, and first feedback means for making the amount of feedback in the reverse direction asymmetric with respect to the amount of feedback from the collector of the second transistor to the bases of the first and third transistors;
And a second feedback means for supplying a collector output of the first transistor to a base of the second transistor.